1. Preheat oven to 400˚F. Have an ungreased 10” tube pan with removable bottom ready.
2. Combine Flour Mix, confectioners’ sugar and zanthan gum and sift 3 times. Set aside.
3. Combine egg whites, cream of tartar, salt, and vanilla in large bowl of an electric mixer. Start at medium and beat until whites are foamy. Gradually increase speed to high adding sugar 2 tablespoons at a time and stiff white peaks form. The volume will double (or more) and sometimes seems as though it will run over the top! Wait for this to happen for the best results. Do not scrape bowl while beating.
4. Fold flour mixture into egg whites in three additions using a rubber spatula. Pour batter into ungreased tube pan. Use spatula to break any air bubbles.
5. Place cake in oven and reduce heat to 375˚F. Bake about 35 minutes until top springs back when lightly touched.
6. Invert cake (upside down – if your pan doesn’t have tabs on the top, you can invert on a narrow neck bottle) to cool completely. Loosen outside and inside circles of cake with a sharp knife. Pull out cake on removable bottom and use knife to loosen from pan bottom. Serve at room temperature. Cannot be frozen. Since it is high in protein and low in fat we eat this cake in the morning for breakfast – if there’s enough left over!